Evidence is accumulating suggesting the effectiveness of yoga with a range of physical health problems. However, yoga is a vast and heterogeneous set of phenomena, and different studies implement yoga in very different ways. This heterogeneity, while reflecting the richness and diversity of yogic approaches, also makes comparison of findings across studies difficult and limits our ability to understand the mechanisms through which yoga therapy affects physical and mental well-being. To advance understanding of the efficacy of yoga therapy, this application proposes to systematically develop and validate a tool to assess dimensions of yoga therapy that can be used across patient populations. Phase I of this 4-phase project will focus on gaining a comprehensive understanding of the relevant dimensions of yoga therapy through a comprehensive literature review and conducting focus group to collect qualitative information from yoga students and instructors. These data will be analyzed using rigorous qualitative methods to identify key conceptual dimensions associated with yoga interventions. Phase II will focus on developing a prototype measure to assess yoga therapy (the Essential Properties of Yoga Questionnaire; EPYQ) and subjecting the prototype to cognitive interviewing. Phase III will involve a large-scale administration of the prototype to refine it through factor analysis and item-response theory. Phase IV will establish the psychometric properties of the EPYQ (i.e., reliability and validity) to produce a final questionnaire. This project is expected to result in the creation of a psychometrically sound questionnaire that can be used in subsequent research conducted on yoga therapies across a variety of patient populations. This measure will allow for future research on yoga interventions to examine the effects of various dimensions of yoga on well-being and to design more sound interventions. Through these four integrated phases, we will achieve three primary aims: (1) Derive a comprehensive listing of potentially central dimensions of yoga interventions (2) Develop a questionnaire that can be completed by objective observers as well as yoga teachers and students to assess the degree to which these dimensions are present in any specific yoga intervention; and (3) Establish the psychometric properties of the questionnaire (i.e., reliability and validity). As a secondary aim, we will, through our literature reviews and collected data, develop a model of potential mechanisms of yoga's effects that may be used in future research on yoga interventions. The creation of a valid and reliable measurement tool for assessing yoga interventions will be valuable for future research in allowing identification and testing of different aspects of yoga therapy and informing selection of appropriate control groups for isolating the therapeutic ingredients in yoga interventions. This research has the potential to improve understanding of how to most effectively translate the results of randomized efficacy trials into clinical practice.